The utilization of automatic dispensers to dispense chemicals used in cleaning processes is well known in the art. Cleaning compositions include compounds such as detergents, rinse aids, softeners, bleaches and the like employed to clean fabrics, dishes and hard surfaces.
The cleaning composition may be a solid detergent in several different forms, including powder, flakes or granular detergent, and pre-shaped detergent briquettes. Another form of solid detergent is the "cast" or block form, comprising detergent that is cast within a mold or a container. Dispensing systems for these solids are known in the art. See, for example, U.S. Pat. No. 4,426,362, issued to Copeland et al. and commonly owned U.S. Pat. Nos. 4,569,781 and 4,569,780 issued to Fernholz et al. The solid detergent is dispensed by spraying a solvent onto the detergent block within the container, thereby dissolving the exposed surface of the detergent to form a concentrated working solution. The concentrated working solution falls into a reservoir or is directed by a conduit to the wash tank of a washing apparatus. When a chemical compound within the container is completely utilized, the exhausted container is discarded, and a fully charged container is placed in the dispenser.
Solid chemicals used in cleaning processes are preferably cast in a sturdy container which can act as a mold, a shipping and storage container, and a dispenser housing. The container may either be retained within the dispenser as the chemical is being used, or the chemical may be removed from the container and placed into the dispenser. However, hazardous chemicals used in cleaning processes such as highly alkaline detergents are preferably packaged such that they can be dispensed without coming into physical contact with the human body.
The advent of high performance products, stimulated in part by increased aesthetic and sanitary standards and a demand for shorter wash times, has generally been characterized by the development of more complex detergent compositions which are more hazardous to the user, less stable, and more difficult to dissolve in a satisfactorily uniform manner. Chemicals used in high performance products, particularly for hard surface cleaning (e.g. ware washing), include alkali metal hydroxides (e.g. sodium hydroxide), phosphates, silicates, chlorine-containing compounds, defoamers and organic polyelectrolyte polymers.
Utilization of solid cleaning compositions has several advantages over the use of pre-mixed liquid cleaning compositions. These advantages include the fact that the solid detergent is easier and cheaper to ship due to its greatly-reduced weight; the solid detergent requires less storage space; and the solid detergent improves the safety of the work environment by reducing possible splashing of hazardous chemicals. Overall, the solid detergent is more convenient for the user, and it permits easy transfer from a container to a dispenser, involving no pouring, spilling or leftover product.
In the past, the containers for the solid detergents have been made entirely of a molded plastic material such as polyethylene or polypropylene. The containers are filled with detergent, stored, shipped to the point of use, and placed into a dispenser. The containers are subjected to extreme conditions such as high moisture, extremely high and low temperatures, and corrosive chemicals. The plastic containers are used only a single time, and then are often discarded to a landfill. These plastic containers sometimes are recycled, but they typically cannot be stacked or collapsed to a compact or flat form.